Electrical heating apparatus



H. N. SHAW March 15, 1932.

ELFCTRICAL HEATING APPARATUS Original Filed Sept. 14, 1928 Patented Mar.15, 1932 UNITED STATES PATENT OFFICE HAROLD N. SHAW, 0F ERIE,PENNSYLVANIA, ASSIGNOR 'I'O GLOBAB CORPORATION, OF NIAGARA FALLS, NEWYORK, A CORPORATION OF NEW YORK ELECTRICAL HEATING APPARATUS Applicationfiled September 14, 1928, Serial No. 305,883.

This invention relates in general to electrical heating apparatus, andit has more particular relation to a certain class of such heatingapparatus, especially such as is adapted for use as a hot-plate ordomestic cooker, embodying or utilizing improved means or devices forelectrically and mechanically mounting or maintaining self-sustainingelectrical resistance heatin elements or units in electrically andmechanically operative position and condition in the apparatus.

In accordance with the present invention, electrical heating apparatusof improved desgn and construction and particularly adapted for use ashot-plates, cookers or heaters and the like, and wherein the productionof medium or relativel high operating temperatures may be desirable, isprovided, such apparatus embodying or utilizing self-sus tainingresistance heating elements, and being especially adapted for use ofsuch elements as are in the form of molded and heathardened bodiesproduced from a composition containing carbon or a carbide, particularlysilicon carbide, as an essential constitucut, and the apparatus alsoembodying improved mounting devices for the heating elements whichinsure efficient mechanical support for the latter and electricalconnection thereof to a supply circuit.

Desirable objects and advantages of the present invention may beattained with electrical heating apparatus, utilizing a combinedelectrical connection and mechanical support for the resistance heatingelement, wherein the combined support and terminal is yieldingly ur edto abut against the ex treme end or on s of the resistance heatingelement with sutficient pressure to satisfactorily insure the desiredresilient mechanical support of and electrical engagement with theheating element, while permitting ready insertion of the heating elementto and its removal from operative position. Additional objects andadvantages, particularly in the matter of sustained efiicient life ofthe heating elements and terminal mountings therefor, are securedthrough utilizing a resistance heating element wherein the termi-Renewed October 19, 1931.

nal portions are rendered of appreciably greater conductivity than thebody portions, because of a different character or composition of suchterminal portions. Further particular objects and advantages areconcerned with the utilization of terminal devices of a yielding butstill of a strong and durable character and their disposition ormounting in such a manner as to substantially remove the more activeresilient portions of the terminal or its support from the region ofgreatest heat, while retaining the other advantages as to structuralsimplicity and improved operation; and additional advantages arerealized through the use of apparatus of this character embodying, inassociation with electrical heating apparatus embodying the yieldingmounting terminals, a supporting structure or frame along with a baseplate thereon, preferably of, or having a surface portion of, refractoryinsulating material and which may be provided with a good reflectingsurface for reflecting heat rays back upon the article or utensil to beheated by the apparatus.

The above and other objects and advantages more apparent from thedisclosure hereinafter are attained by the present invention, variousnovel features of which will be apparent from the description anddrawings herein, disclosing several embodiments of the invention, andwill be more particularly pointed out in the claims.

in the accompanying drawings showing heating apparatus embodyingfeatures of the present invention:

Fig. 1 is a view in sectional elevation of one form of electricalheating apparatus embodying the present invention.

Fig. 2 is a broken plan view showing a further modified form of thepresent invention.

Fig. 3 is a broken sectional elevation in the plane of a horizontalcenter line of Fig. 2.

In the embodiment of the invention disclosed in Fig. 1, a base 11, whichmay be considered of refractory insulating material, is carried by orforms a part of an enclosing boxlike frame 13. Contact terminals 14 aremounted on the base or support 10 adjacent 'the side ed es thereof, andinclude a relative ductive material secured, by riveting, welding orotherwise, to the supporting leaf or strap spring 15. The inner side ofthe contact strips 21 at the upper ends thereof, and, if desired, thecorresponding portion of the supporting leaf spring 15, are providedwith concavities or recesses, as indicated, for eas or adjustablereception of the ends of sel sustaining resistance heating elements 24which have butt-end engagement with the walls of the recesses.

At a point intermediate the contact terminals 14., an upright support 26is secured upon the base 11, this support being shown as of conductivematerial and suitably insulated by a separator 27, preferably of aslightly yielding character, from the base 11. The upri ht support 26may be secured in position y a screw .or bolt 28 passing through anaperture in the base 11 and threaded into the lower end of the support,the head and shank of the screw being spaced from the base 11, as bmeans of a flanged bushing 29, as of somew at yielding insulatingmaterial. There is mounted on the upper end of the support 26 aconductive block 31 of suitably heat-resistant material, the same beingprovided with a suitable number of recesses intended for the easy oradjustable reception of terminal portions of heating elements 24 whichhave butt-end engagement with the walls of the recesses, the oppositeends of the heating elements being supported by and in yielding andreleasable operative engagement with the terminal mountings 14. Thelower end of the bolt or screw 28 may have provided thereon a metallicwasher 41, a

line connection 20 being indicated as being held in position betweenthis washer and the upper face of the head of the bolt 28 or a metalwasher thereon.

The shank portions 15 of the mounting or supporting terminals 14 passthrough openings 51 in the base 11, and are bent at right angles attheir lower ends, the bend belng preferably along a wide easy curve soas to distribute bending strains; and the horizontal p'ortion at thelower end of the terminal is secured to the under side of a block orstrip 52 of insulating, and preferably refractory, material. Thissupporting block 52 is suitably secured to the under side of the base 11at spaced points, as by headed bolts 55 passing through both memberswith securing nuts thereon, as indicated at the ri ht in this figure,near but still substantial y spaced from the inner edges of theapertures 51 through the base. ach terminal may be secured in operativeposition by means of a screw or bolt 16 passing through an aperture inthe insulating block 52, and having its head disposed in a counter-boredportion of such aperture, a nut 18, with or without an intermediarywasher 17, serving to clamp the terminal in operative position and abentover portion 53 at the inner end of the horizontal portion of theterminal bearing against the inner side of the block 52, thus serving toprevent the terminal from displacement through rotation. A nut 19 servesto secure a line terminal 20 in operative connection with the terminal15. By reason of the fact that the contact supporting block 52 ismounted in position on the base 11 independently of the screws or bolts16 which se cure the terminals 14 in position, it is possible toassemble a group of terminals as a unit, these terminals passing throughthe apertures 51 in placing the block 52 in operative position. v

The outer relatively stifi' and resilient sup porting strips 15 of theterminals 14 are preferably so formed as to include one or morestiflening ribs 56, here indicated as a pair of spaced ribs provided byturning back at right angles integral side portions of the strip 15,these ribs tapering in width toward the lower part of the strip where itpasses through the opening 51 in the base plate. The ribs 56 contributetoward maintaining the strength and resilience of those portions of thestrip 15 which are more exposed to the heat produced by the heatingelements 24;, these desirable effects of the ribs 56 being supplementedor accentuated by reason of the effect of these ribs in greatlyassisting in dissipating heat from the body portion of the strip 15 andthe contact strip 21 secured thereto.

It will be apparent that the mounting of the terminals 15 is such aspermits ready resilient displacement of the upper contact ends thereoffrom normal operative position, such as may be incident to the removalof a heating element from and its replacement in operative position; andthe desired security of electrical and mechanical mounting of theheating element is attained as in the other heretofore describedembodiments of the invention; and there is the additional advantage thatthe actively resilient portions of the terminals are disposed at pointswhich are out of. the region of greatest heat and support may be omittedand a single heating element substituted for the two heating elements24.

In accordance with the disclosure of Figs. 2- and 3, a refractoryinsulating base plate made up of a central portion 62 and two sideportions 63, is rovided with through passages 64 from t e upper to theunder side, these through passages being preferably formed by thesuitable conformation of one or both of the adjacent edges of the parts62 and 63 of the base plate. The base plate is removably disposed uponthe bottom of a box-shaped frame 65 having an outer flange 67 at itsupper edge, the same being adapted to rest upon an inwardly turnedflange 68 formed about an aperture in the range top or like support 69,the cooperation between the flange 67 and the flange 68 being such as toinsure removable support of the boxlike frame 65 in operative position.

The terminal members 1 1 are of the same general character and aremounted in operative position in the same manner as the correspondingparts of Fig. 1, the bottom of the box or supporting frame 65 beingapertured in alinement with the apertures 64 to permit the shank portion15 of the terminal to pass therethrough. The supporting block 52 ismounted in o erative position by means of screws or bolts 6 having theirheads disposed in counter-bored portions of through recesses in theblock and passing through apertures in the bottom of the supportingframe 65, nuts 7 8 being applied to the upper ends of said securingbolts and serving to draw said block into and secure the latter inoperative position against the under side of the bottom of the frame 65.The under side of the center portion 62 of the base plate is suitablyrecessed to receive the upwardly projecting portion of the securingscrew or bolt 76 and the retaining nut 78 thereon, thus permitting thebase plate to rest flush on the bottom plate of the frame 65.

The upper face of the base plate, particularly the center portion 62thereof, is preferably inclined from all sides toward the center so asto provide a cup-shaped upper surface, a central aperture 81 through thebase plate serving to drain the lowest portion of this cup-shapedsurface, and the upper surface of the base plate is preferably providedwith a high glaze of a heat-resistant character so as to serve as anefficient reflector of heat rays.

It will be apparent that the heating elements 24* which are disposedrelatively close to the reflector on the refractory base plate may bereadily removed from and replaced in operative position between theterminals 14, with their strengthening ribs 56, as has been describedhereinabove. Likewise, with the heating elements removed from operativeposition, it will be apparent that the several sections of the baseplate may be removed upwardly from operative position, as for purposesof cleaning, these sections of the base plate readily passing by theupwardly extending terminals 15, by reason of the provision of theapertures or recesses 64.

A removable apertured top plate 83 is provided relatively close to theheating elements 24 the same preferably being provided with ribs 84extending toward each other from opposite side portions of the plate andstaggered with respect to the heating elements 24*. This plate 83 servesas a support for a utensil to be heated, and it is preferably supportedin operative position by having its edge portions resting upon theflange 67 at the upper edge of the box-like frame 65, the flange 68 ofthe range top 69 or like support being sufliciently depressed so thatthe upper surfaces of the range top and the removable top plate 83 arein the same plane. In order to insure that the removable top or coverplate 83 occupies the same position at all times, that is, with the ribs84 at the opposite sides of and parallel to the heating elements, thetop plate may be provided with a depending projection 85 bifurcated atits lower end so as to pass over a projection 86 extending inwardly fromthe side wall of the box-like frame 65.

The resistance heating elements 24 and 2? are preferably unitary,self-sustaining, molded and heat-hardened composition products wherein acarbonaceous material, such as silicon carbide, is the principalconstituent. Certain heating elements of the preferred character areknown in the art, the same being composed of silicon carbide as anessential constituent, with or without one or more modifying substancesfor altering mechanical or electrical characteristics of the finalproduct. The preferred heating element comprises a heat-producing bodyportion and lntegral terminal portions of the same crosssectional areaas the body portion but of such different composition as to be possessedof greater conductivity and less heat-producing effect than the bodyportion, but still of such a character as not to he possessed of anymechanical or electrical weakness because of these portions ofdiflerentcomposition. This presence of more highly conductive terminalsinsures that portions of the metallic terminal mountings in electricaland mechanical engagement with the ends of the heating element aremaintained in satisfactory operating condition during a long lif' Asindicated, the conductive terminal mountings described hereinaboveinclude means for resiliently or yieldingly supporting the heatingelement and maintaining the desired electrical connection from a linecircuit to the ends of the heating element, wholl through butt-endengagement between the heating element and the terminal mountings; andthis resilient effect may be present in one or both of the terminalmountings. This desired yieldin but still forcible, butt-end contactrelation etween the end of the heating element and the contact portionof the termi- 5 nal mounting is secured through the resilience toryresilient and heat-resistant materials for the circumstances.

producing the desired resilient supporting effects in the terminalmountings are tempered steel, or an iron-chromium alloy, such ashardened ascoloy, or an aluminum-iron-copper alloy, such as alcumite oran iron-nickel chromium alloy such as ca-lite; and likewise with theseresilient parts of suitable cross-section, they serve efiiciently as aportion of the electrical path through the terminal mounting.

Where the operating temperatures of the heating appliance are relativelylow, the recessed contact portion of the terminal mounting may be ofaluminum, or an alloy thereof, such as aluminum-nickel, which does notoxidize or scale to a distinctive extent under However, wheretemperatures produced are higher or approach or exceed the melting pointof aluminum, nickel or chromium or iron-chromium-nickel alloys, oraluminum-nickel alloys, give desirable results. Aluminum allo contactsfor electrical resistors are describe in an application by John A.Boyer, U. S. Serial No. 386,998, filed August 19, 1929.

The present invention is especially concerned with the provision ofapparatus capable of commercially satisfactory and efficient operationat temperatures corresponding to a glowing condition of the resistanceheating element; and electrical heating appli- A set forth herein is notlimited to the exact ing heating element is electrically and me- 7chanically mounted in operative position through yielding butt-endengagement of a contact portion of the terminal with an end of theheating element, comprising a supporting portion of resilient conductivestrip material having an edge portion turned back at an angle to providea strengthening rib and means for conducting an electric current to saidterminal.

2. A terminal for an electrical heating appliance of the'ty e wherein aself-sustaining heating element is electrically and mechanically mountedin operative position through yielding butt-end engagement of a contactportion of the terminal with an end of the heating element, comprising asupporting portion of resilient conductive strip material having an edgeportion turned at an angle to the original strip to provide astrengthening rib, the ribbed portion of the terminal being carried by aresilient portion.

3. The terminal described in claim 2 in which the resilient portioncomprises an extended strip bent through a wide angle from the ribbedportion.

4. A terminal for an electric heating appliance of the type wherein aself-sustaining heating element is electrically and mechanically mountedin operative position through yielding butt-end engagement of a contactportion of the terminal with an end of the heating element, comprising asupporting portion of a conductive strip, a portion of said strip beingrigid and another portion of the said strip being resilient, the rigidportion of the said strip being adjacent the terminal portion of theheating element, the resilient portion of the stri being more remotefrom the end of the heating element than the rigid portion of the strip.

In witness whereof I aflix my signature hereto.

HAROLD N. SHAW.

